Australia has a good system (at least here in Victoria - different states vary). The ultimate goal is to produce a percentile ranking of students (as opposed to an absolute GPA), and to that end, classes are weighted by the quality of students taking them (as measured by a state-wide general test) and the final exams are all standardized. Plus, only the top 6 scoring subjects taken count (and only the top 4 scoring count fully), eliminating that issue.
